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|What to look for in a capacity management tool|
In addition to database reporting, most vendors offer tools that report on what switch ports are free and used, what volumes on storage arrays are allocated and unallocated, and how much traffic is traversing the SAN. How well each product does this depends on how it is architected, and if the vendor integrates this function into their overall reporting.
The products that best integrate these reports have the largest agents and invariably the most complicated installs. However, this is changing as newer, better-designed products with small agents can get the world wide name (WWN) off of a server's host bus adapter (HBA) and with only that information, can identify that WWN's path through the SAN and any and all of the storage assigned to that WWN on any storage array. Older products use more cumbersome methods to gather this same information.
For instance, products such as CreekPath System's Storage Operations Manager, EMC's Control Center and Veritas' SANPoint Control collect this information by putting agents on every server attached to the storage network. Their agents perform active monitoring on the servers on which they reside, querying the server and SAN for updated information based upon parameters set up by the user. Because these agents remain active on the server, users need to determine how current they want their information to be--how often the agents should run. Additionally, they need to consider the time it will take to configure the agents of these products and whether they will realistically be able to use all of the information that these products provide. Better to look for products whose agents can be deployed and configured in less than two minutes. Anything longer than two minutes is not worth the effort.
Tape utilization and library monitoring remains below most users' radar screens. Products like Storability's GSM do give visibility into StorageTek's tape environments and most tape vendors provide native utilities to measure and report on library capacity. Yet with the increasing use of ATA disk backup, the relatively low cost of tape and the scarcity and proprietary nature of tools that manage tape, users should concentrate on getting disk under control before worrying about tape.
Measuring the assets
The time it takes to measure storage assets will depend on the tool selected, the size of the environment, what's being measured and the number of agents deployed. All of these factors will contribute to the quantity, quality and level of detail gathered on the environment. Users should temper their reporting expectations in accordance with how long the tool has been implemented. Depending on the components deployed, expect initial reports to provide statistics on storage utilization, the sizes and types of files on individual servers, available ports on FC switches and allocated and unallocated storage on each storage array.
These usage reports can have immediate impact on the bottom line. It will help organizations determine if they need to purchase more storage arrays or switch ports, if they have enough available to meet current and forecasted needs or if they are buying the right kind of storage. For instance, the reports may confirm that the organization may need to purchase more storage. However, it may also reveal that the storage needed doesn't need to be an expensive monolithic array, but a more affordable modular array because the data is primarily reference data.
After the tool is up and running for a few months, expect more comprehensive enterprise reports. Storage utilization may now be grouped by such criteria as application, operating system, location or department.
Making information life cycle management (ILM) a reality requires intervention. Actively managing your storage to achieve an effective ILM program should be an important consideration in choosing a capacity management tool. Right now, only the best managed environments can report on and measure storage capacity but they remain hard-pressed to redeploy storage assets quickly. Next-generation technologies such as newer storage arrays, iSCSI SANs and network-based file- and block-based virtualization, along with host-based replication software will help organizations realize the benefits of a centrally managed storage utility.
This was first published in March 2004